Recently, a BiCS (Bit Cost Scalable) that is a next generation type NAND flash memory is developed. The BiCS is fabricated by stacking memory cells in a multistage form in a three-dimensional direction. In the BiCS, densification of the cells still remains as a matter to be settled. Although it is conceivable to dispose memory holes in a staggered form in order to densify the cells, in this case, there is formed a part where a distance between adjacent plugs becomes considerably short. As a result, there is such a disadvantage that a bit line capacitance of that part is considerably increased.